The invention discloses a CNN (convolutional neural network) construction method. The CNN construction method comprises the following steps: a unitization instruction is received, according to the unitization instruction, hardware resources for convolutional operation are configured into a convolutional unit, hardware resources for activating operation are configured into an activating unit, and hardware resources for pooling operation are configured into a pooling unit; a configuration file is read and contains convolutional unit configuration parameters, activating unit configuration parameters, pooling unit configuration parameters, the number of convolutional layers and the number of full-connection layers; the convolutional unit is configured according to the convolutional unit configuration parameters, the activating unit is configured according to the activating unit configuration parameters, the pooling unit is configured according to the pooling unit configuration parameters, and the number of the convolutional layers and the number of the full-connection layers are configured, so that the CNN is constructed. The invention further discloses a CNN construction system. The CNN construction method is high in construction efficiency.